The FBI has searched a post office close Miami, as investigators endeavor to discover who
is behind a progression of suspected explosive bundles presented to Obama, Clifton and others.
Gadgets have been sent to eight prominent individuals, including ex-President Barack Obama and actor Robert De Niro.
Unnamed officials told US media that investigators believe at least one was sent from Florida.
The FBI have not released any details of their investigation.
Similar packages have also been sent to former Vice President Joe Biden and former Secretary of State Hillary Clinton, among others.
The postal facility searched is in Opa-locka, where security footage was being scrutinised. A bomb squad and canine unit accompanied federal officials, Miami-Dade County Police said.